STUTTGART, Germany — Top-ranked Naomi Osaka came from behind in the final set to beat Donna Vekic 6-3, 4-6, 7-6 (4) on Friday and reach the semifinals of the Porsche Grand Prix.

Osaka easily won the first set before Vekic looked to have seized control of the match by winning the second and building up a 5-1 lead in the third.

But Osaka, who twice was two points from defeat, regrouped to win five straight games and force the tiebreaker, which she wrapped up after two early mini breaks. The win sends her into her first semifinal since winning the Australian Open in January.

"It means a lot I think, especially since it's clay," Osaka said. "I spent a really long time after Miami just training on clay, trying to get comfortable with it, and I'm really happy that that paid off."

Osaka will next face eighth-seeded Anett Kontaveit of Estona, who moved on when Victoria Azarenka retired with an injury.

Kontaveit led 3-0 in the third set when Azarenka was forced to quit with an injury that affected her service motion.

Third-seeded Petra Kvitova of the Czech Republic came from behind to beat Latvia's Anastasija Sevastova 2-6, 6-2, 6-3 and reach the semifinals for the third time.

"It's nice to be in the semifinal again. It's still a lot of work to do," Kvitova said. "I didn't reach the final here yet, so hopefully this time will be better."

Kvitova will play Kiki Bertens of the Netherlands, who beat Germany's Angelique Kerber, a two-time champion in Stuttgart, 6-3, 6-4.

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